Effects of temperature and filler content on the creep behaviour of a polyurethane rubber

Abstract

Both elastic stress-strain testing and (primary and secondary) creep testing have been carried out on un-reinforced rubber and on two particulate-reinforced rubber composites. This has been done at three differenttemperatures for all three materials. The stress-strain curve of the rubber conforms well to that expected fromclassical rubber elasticity theory. When expressed as true stress–strain relationships, all three materials exhibitapproximately linear plots, with the increases in stiffness on adding the particulate conforming to compositeelasticity theory. The creep behaviour of all three materials can be captured well using a Miller-Norton for-mulation and the observed dependence on temperature has been used to estimate the activation energy for creepto be ~7 kJ mole-1. This is thought to indicate that the creep process does not involve rupture of covalent bonds(for the range of applied loads used), but is associated with physical processes such as molecular untangling. Thefillers do enhance the creep resistance, to a degree that is quantitatively consistent with the expected loadtransfer from matrix to particulate.